The brain and spinal cord are encased in the cranium and vertebral column inside a thin membrane known as the meninges. The space within the meninges includes, among others, the ventricles, and CSF is produced in the chorioid plexus in the ventricles at a rate of 0.3-0.4 ml/min under normal conditions.
CSF flows through the ventricles, aqueduct and basal cisterns over the cerebral surface to the arachnoid villi, from where the CSF is absorbed into the sagittal sinus (including sinus transversus). However, in subjects suffering from hydrocephalus, CSF drainage is hindered, and CSF shunting is required to provide a sufficient drainage.
Prior art shunt devices have a relatively short lifespan due to multiple factors, including e.g. obstruction of the drain, and shunt deficiencies resulting e.g. in excess drainage of CSF.
Obstruction of a shunt device may be complete, partial, or intermittent. If the obstruction is only partial or intermittent, an individual may experience periodic headaches, nausea and vomiting, drowsiness, listlessness, loss of appetite, and a general decrease in mental functioning.
Complete obstruction of a shunt device may cause the same symptoms, as well as more severe signs of blurred vision, loss of coordination, and possible loss of consciousness.
Obstruction may be a consequence of an encapsulation of the shunt device in the form of endothelialization of the shunt outlet by endothelial tissue, which envelops around the outlet, and forms a barrier capable of impairing or arresting drainage.
Overdrainage often results when CSF is shunted to the peritoneal cavity when the pressure difference between the inlet and the outlet ends of some prior art shunts is too high. The difference in pressure results in very low, or even negative, intracranial pressure, and this may in turn result in a collapse of the ventricles, or even subarachnoidal effusion of blood and subdural haematoma.
Several attempts have been made to alleviate the above-cited problems, including the provision of a surface coating, as explained in US 2007/0112291A1. However, even though use of a surface coating may in some cases provide an improvement, most shunt devices in use today still have to be replaced within 5 years of insertion.
WO 2015/108917 discloses a shunt device and methods for fixing the shunt device directly to a wall of the sinus system during use. WO 2015/108917 does not teach or suggest a shunt device having a distancer for maintaining a certain minimum distance between an outlet end of a tubular outlet element and endothelium surrounding said tubular outlet element, preferably without making any contact with said endothelium.
There is a need for shunt devices which may be inserted over longer periods of time, and which are less likely to be obstructed as a result of contact between elements of the shunt device and surrounding tissue, including endothelial tissue of the sinus system, including vena jugularis.